Brown algae on gravel

[adamsfour]

Hello
I have a 100 gallon Reef tank. Been running many years. A few months ago I had a outbreak of Red Algae which I successfully remove with Chemiclean. Since that point I have had an increase in Brown algae on gravel. Not out of control but noticeable. Not sure it’s related. Also large number of large coral which I am speculating is shielding the light. My level are Calcium 420, Alk 9.5, mag 13. Ammonia 0, nitrate and nitrite close to zero. 10 percent water change per week. Any ideas

 

[fishface NJ]

photo would be great with white lighting on. You must be careful not to get dinos with your nitrates close to zero. What are your phosphates?

 

[adamsfour]

Here’s my take last test
Ammonia NH3 - 0.0 ppm
Nitrite NO2 -0.0 ppm
Phosphate PO4 - 0.0 ppm
Nitrate NO3 - 8 ppm
Will post picture ASAP

thanks